This invention relates to the field of chimney and fireplace constructions in general, and more particularly, to the field of chimneys and fireplaces having internal chambers to increase the drafting effects of the chimney or fireplace.
In any situation where incineration or burning is to take place inside a building, such as in foundries, mills, trash incinerators or home fireplaces, it is necessary to provide conduit means for removal of the smoke, gases and excess heat outside of the building. The most common mechanism is to provide a chimney structure. Since the incineration process creates a heat differential, drafting occurs because the hotter air will rise and exit out the top of the chimney. In constructing incinerators, furnaces or fireplaces, the size of the firebox area and the amount of draft required must be taken into effect when designing the size and structure of the chimney. The chimney must be able to draw out and remove all of the smoke and gases or the fireplace or incinerator cannot function in a house or factory.
A typical furnace set-up in a factory involves a large firebox area where high temperature combustion on a large scale occurs. Chimneys must be large volume and substantial in height to remove the smoke, gases and excess heat. Since the principle behind the drafting effect is the temperature differential, these large chimneys encounter problems in efficient drafting due to the temperature drop as the distance from the firebox increases. An additional problem is the build-up of soot, creosote or other by-products on the interior of the chimney, caused by the adherence of these by-products to the relatively cooler upper walls of the chimney. Periodic shut down of the furnace or incinerator is required to remove these hazardous flammable materials from the chimney.
A home fireplace must both contain the fire and draw the smoke up through the chimney to the outside. Efficiency in removing the smoke is of prime importance, and fireplace constructions involve specific dimensional relationships between the different components parts to insure that the job is accomplished. The size of the firebox area, the smoke chamber and the chimney flue are all related. Improper ratios among the components will reduce the efficiency of the fireplace. Other factors which affect the drafting ability of a fireplace, as well as incinerators and furnaces, are atmospheric conditions and materials. For example, high altitude locations require certain adjustments due to lower barometric pressure. A fireplace that drafts well at sea level may not draft effectively in the mountains. The materials used in construction also affect the drafting efficiency of a fireplace. Since drafting is a result of the heated air rising through the chimney and exiting the building, a fireplace constructed all or in part of metal will be a "colder" fireplace than one made of refractory brick or ceramics, and will draft less effectively. The refractory materials will remain warmer than the metal, thus contributing to heating the air even in the smoke box and chimney areas.
Because of economic factors and ease of construction, many builders now prefer metal fireplace units over refractory material fireplaces. As stated, this can result in problems due to inadequate drafting, which are especially aggravated in high altitude or multi-story applications. Furthermore, such metal constructions are more hazardous due to corrosion effects, and fire code restrictions are being added in many areas.
It is known to increase drafting in home fireplaces by creating hollow walls in the firebox materials, such hollow portions opening into the smoke chamber or chimney and having vents which open into the internal room to draw in air. See, for example, U.S. Pat. No. 710,226 to Vitti. The heat in the firebox warms the hollowed walls and rising heated air exits through the chimney, and this heated air is replaced by drawing cool air from the room through the vents. This method is not desirable since the air drawn from the room through the vents vastly decreases the overall heating efficiency of the fireplace. Furthermore, the air drawn in is not heated to as high a temperature as desired, since only a slight temperature difference over the outside air temperature will result in the drafting effect. Thus the air added to the smoke chamber or chimney area will not be of high enough temperature to greatly affect the drafting ability of the fireplace, and the lower temperature air contained in the fireplace itself is not affected. Also, large hollow portions will reduce the strength of the structural materials, which means that the fireplaces must be constructed of small size.
This invention solves the problems outlined above by providing a number of vertical air chambers within the walls of the firebox area or the lower chimney itself which are not vented outside the firebox or chimney. The air chambers open only into the smoke chamber or chimney, thus insuring that only high temperature air is added to the drafting flow coming from the main firebox, since there is no channelling of outside air into the system. The heated air rising from the air chambers is replaced by the relatively cooler, draft inhibiting air contained within the fireplace itself. The heating efficiency of the fireplace is not affected since no additional air is removed from the room. The air chambers are elongated vertically to maximize their volumes while at the same time not detracting from the overall strength of the structure. Because the air chambers supply high temperature air to the smoke chamber or chimney to increase the draft, problems associated with altitude and atmospheric pressure are alleviated. Additionally, fireplaces can be constructed with the lower portions made of refractory materials while constructing the chimneys out of cost-effective and light-weight metal, since the added drafting compensates for the "cold" material. The air chambers also act to insulate the exterior walls of the firebox itself by acting to disperse the internal heat built up within the walls.
It is an object of this invention to provide a means for increasing the drafting ability of a fireplace or furnace chimney by the use of vertical air chambers contained within the walls of the firebox or lower chimney.
It is a further object to provide such means which does not draw cool air from inside the building.
It is a further object to provide such means where the air chambers open only into the smoke chamber or chimney area.
It is a further object to provide such means within either modular pre-constructed fireplace assemblies or on-site, handbuilt fireplaces.
It is a further object to provide vertical air chambers to increase drafting as an add-on feature to existing fireplace or furnace constructions.